1. The equation X^5 - 2X^4 - X^3 + 6X - 4 = 0 has a repeated root at X=1 and a root at X-2. By a process of division and solving a quadratic equation, find all the roots and hence write down all the factors of X^5 - 2X^4 - X^3 + 6X - 4
2. Given that cosX= (e^jx + e^-jx)/2
sinX= (e^jx - e^-jx)/2j
using only this information, prove that 2cos5xsin2x = sin7x-sin3x